The present invention relates to an integrated starter generator (ISG) device comprising a housing, a stator and a rotor contained within the housing. The device is preferably used in motor vehicles but may also be used in other applications. It is preferably mechanically coupled, via a pulley, to the ancillary belt of such a vehicle.
As the demand for electrical power in vehicles has increased, the trend in alternator (generator) design has been towards greater power capacity. At the same time there has been a requirement to make the alternator housing more compact, such that it takes up less space in the vehicle's engine bay.
Furthermore, a growing need for the reduction of fuel consumption by the internal combustion engine has led to the development of the Integrated Starter Generator (ISG), which represents an alternative to the conventional alternator. Like an alternator, the ISG generates electric power when the engine is running, for supplying the vehicle's electrical system and charging its battery. However, the ISG combines the functions of the conventional alternator/generator with those of the starter motor in a single ISG. Thus, it is capable of being switched from an alternator mode to a starter mode and vice versa. The weight of the ISG is typically less than that of the combined weights of separate alternator and starter motor components and the ISG can automatically stop and then rapidly restart the engine to avoid periods of unnecessary engine idling, such as when a vehicle is waiting at a traffic light. This reduces fuel consumption and exhaust emissions. Furthermore, in starter mode, the ISG is able to spin the engine at higher speeds than a conventional starter motor which further aids in fuel efficient and more reliable starting of the engine.
Like an alternator, the ISG includes a stator and rotor. However, the dual function of the ISG described above means that it requires other components in addition to those usually found in an alternator. In particular, the ISG includes various electrical components for producing the high current needed for starting the engine. Furthermore, complex electronics are necessary to control efficiently the start-stop function of the ISG or to communicate with the engine management systems of a vehicle. Moreover, the ISG faces the same requirement for compactness as the conventional alternator.
A typical belt-driven ISG (BISG) has a housing containing a rotor and a stator. The electrical connections for the rotor and stator exit the housing and lead to a separate control unit which is preferably located nearby. The rotor and stator electrical connections typically carry high currents of the order of several hundred amps and in a switched reluctance arrangement are also switched many thousands of times a second during operation. Thus the cabling between the ISG housing and the control unit is bulky, inflexible and heavy because of the high current requirements, and presents a significant EMC challenge due to the rapidly-switched high currents flowing in the cables. Furthermore, the relatively long cabling introduces electrical losses. Also, the need to mitigate these problems by minimizing the length of the cabling and mounting a control unit near to the BISG in what is typically a crowded area of an engine bay, presents further challenges. These aspects of conventional ISGs have hindered the uptake of these devices despite their significant advantages.